Oh and "painting": This may be the easiest way to repair this...spray/blend/clear. As mentioned I have a guy who works wonders and works on NEW bmws everyday. He's a E92& E28 M5 owner who works at my local BMW dealership (I call him the body shop wizard!)
The ding is right above the belt line rear quarter panel/pass side. It's right above the rocker panels.
--And for those confused in size of the ding; It's super small. Literally the size of this (). <-Actual size I think a rock kicked up and hit there, causing the ding. No way is it a door ding..
Thoughs about paintwork: spot-blending....
1988 325i sedan (Cirrus Blue Metallic, Silver Grey Leather)
2011 128i convertible (Blue Water Metallic, Grey Leather) -Gone-
2013 320i sedan Sapphire Black Metallic, Black/Black